1. Field of the Invention
The present invention relates to a method for rectification and apparatus therefor.
2. Description of the Prior Arts
FIG. 10 is a explanatory view of an prior art rectifying column. Prior art rectifying column 1 will be described with specific reference to FIG. 10. A plurality of plates are arranged inside column body 2. Raw material feeding pipe 4 is mounted on the middle level of the column. Steam pipe 6 for heating hold-up is connected to bottom portion 5 of the column. On the other hand, reflux tank 8 is arranged for condensing a vapor from the top of the column and refluxing a part of the resultant by condensing the vapor. In reflux tank 8, there are arranged refluxing pipe 9 for refluxing condensed components of low boiling point, offtake pipe 10, through which a product is taken out, and drain pipe 12 for draining condensed water. Further, there is arranged second offtake pipe 11 for taking out components of high boiling point as bottoms from bottom portion 5 of the column.
The operation of rectifying column 1 constructed as described above will be explained. A hold-up is heated by blowing a steam from steam pipe 6 in bottom portion 5 of column 1. A part of the hold-up is made to rise as a vapor and brought into counter-current contact with a refluent fluid from the upper side of the column on each plate 3 thereof. In this way, condensation of the vapor and revaporization of a liquid obtained by the condensation of the vapor are repeatedly carried out. Components of low boiling point are taken out from the top of the column. A distillate condensed by means of condenser 7 is charged into reflux tank 8. Water obtained by condensing vapor is discharged from drain pipe 12. A part of the distillate is returned through refluxing pipe 9 to column body 2 and the other part thereof is recovered as a top-product through offtake pipe 10. Further, components of high boiling point as bottoms are taken out from bottom portion 5 of the column through second offtake pipe 11.
Operations have been carried out in the prior art rectifying column without any remarkable difference in heating energy charged into each of the compartments as far as there is no great difference in hold-up accumulated in each of the compartments of a rectifying column. It is pointed out that the reason is that the operations of the rectifying column of the prior art could be sufficiently carried out only by simply charging energy into the rectifying column without controlling charged energy so that there could be difference in the charged energy.
Actually, the amount of heating energy charged for obtaining a predetermined rectifying performance has an effect on an operation cost of the rectifying column. It is known, for example, that the compositions of liquids accumulated in each of the compartments of the rectifying column is usually various, and that the liquids in the first of the compartments are rich in volatile components. It is useless in terms of energy saving to charge the heating energy into each of the compartments without any consideration.
In the prior art rectifying system, products beyond the range of a specification have been taken out from the rectifying system until the operation condition of the rectifying system is determined by repeating an increase and decrease of heating energy by the method of trial and error to attain a predetermined rectifying performance, for example, to obtain a product of a predetermined specification from the top portion and the bottom portion of a rectifying column. The increase of the yield of the product ceases inevitably, however, until the operation conditions are determined. This has been a great problem in rectifying columns, in which the components of feed are very often changed.